thorium

thorium
source
Name	Thorium
Atomic number	90
Atomic mass	232.0377
Category	Actinide
Appearance	Silvery metallic
Discovered	1829
Discoverer	Jöns Jakob Berzelius
Phase	Solid
Melting point	1750 °C
Boiling point	4820 °C

thorium

Thorium is a naturally occurring, radioactive, silvery actinide metal notable for its potential role in advanced nuclear reactor concepts and its historical uses in industry. It was identified in the 19th century and has been linked to figures and institutions in early radiochemistry and industrial chemistry. Contemporary interest spans research at national laboratories, technology companies, universities, and energy policy bodies exploring alternative fuel cycles and materials applications.

Introduction

Thorium is an actinide element with complex links to the work of chemists and institutions such as Jöns Jakob Berzelius, Marie Curie, Ernest Rutherford, Otto Hahn, Fritz Haber, Max Planck, University of Stockholm, KTH Royal Institute of Technology, University of Paris, and University of Cambridge. Its discovery and early study intersect with laboratories and museums like the Swedish Museum of Natural History, Royal Society, Smithsonian Institution, Natural History Museum, London, and industrial houses including DuPont and General Electric. Policy and research involving thorium have been shaped by organizations such as the International Atomic Energy Agency, United States Department of Energy, European Commission, and national laboratories like Oak Ridge National Laboratory and Lawrence Livermore National Laboratory.

Properties

Thorium is a dense, high-melting-point metal with metallic bonding and typical actinide electronic structure studied by groups at Max Planck Institute for Chemical Physics of Solids, Los Alamos National Laboratory, Argonne National Laboratory, and Lawrence Berkeley National Laboratory. Its most common isotope, thorium-232, has a very long half-life and decays via alpha emission, a property characterized in work at CERN, Brookhaven National Laboratory, and the Royal Society of Chemistry. Metallic thorium oxidizes in air and forms thorium dioxide, a refractory ceramic investigated by researchers at Massachusetts Institute of Technology, California Institute of Technology, and Imperial College London. Crystallography and electronic properties have been examined using facilities such as the European Synchrotron Radiation Facility, Diamond Light Source, and Brookhaven National Laboratory (BNL) Relativistic Heavy Ion Collider.

Occurrence and production

Thorium occurs in minerals like monazite and thorite and is mined in regions associated with companies and states including India, Brazil, Australia, Norway, United States, Sri Lanka, and Madagascar. Major mineralogy work linking thorium-bearing ores involves institutions such as the Geological Survey of India, United States Geological Survey, Brazilian Geological Survey (CPRM), Norwegian Geological Survey, and university geology departments at University of Queensland and University of Edinburgh. Extraction and processing technologies have been developed by corporations and labs including Rio Tinto, BHP, Vale S.A., Thomson Reuters, Kennecott Utah Copper, and research projects funded by the European Atomic Energy Community and national research councils.

Applications and uses

Historically, thorium compounds were used in incandescent mantles, gas lamp mantles developed by inventors and firms such as Carl Auer von Welsbach and companies like General Electric and Osram. Thorium dioxide has been used in high-temperature ceramics, optical lenses, and catalysts studied at BASF, Dow Chemical Company, and academic groups at Stanford University and ETH Zurich. Thorium alloys have been investigated for aerospace and military applications by agencies including NASA, United States Air Force, and defense contractors like Lockheed Martin and Northrop Grumman. Scientific instrumentation containing thorium has been used in precision optics, electron microscopy, and specialized electrodes with contributions from Zeiss, Thermo Fisher Scientific, and FEI Company.

Thorium in nuclear energy

Thorium-232 can absorb neutrons to breed fissile uranium-233, a process researched in programs at Oak Ridge National Laboratory, Argonne National Laboratory, India's Department of Atomic Energy, China National Nuclear Corporation, Vikram Sarabhai Space Centre, Rosatom, and corporate ventures such as Thor Energy and startups collaborating with European Commission projects. Reactor concepts using thorium feedstocks include molten salt reactors, heavy-water reactors, pebble-bed reactors, and accelerator-driven systems explored at Flibe Energy, Moltex Energy, Terrestrial Energy, Copenhagen Atomics, China Academy of Engineering Physics, ThorCon, and research consortia funded by ITER-related organizations. International debates over proliferation risk and safeguards involve International Atomic Energy Agency protocols, export-control regimes, and non-proliferation bodies like the Nuclear Non-Proliferation Treaty signatories and national regulatory authorities.

Health and environmental effects

Thorium and its decay products pose radiological hazards documented by public health agencies such as the World Health Organization, Centers for Disease Control and Prevention, Environmental Protection Agency (EPA), and occupational safety bodies like Occupational Safety and Health Administration (OSHA). Environmental monitoring and remediation programs have been conducted by organizations including the United Nations Environment Programme, International Commission on Radiological Protection, National Institute for Occupational Safety and Health, and regional agencies in mining countries. Historical occupational exposures were described in literature connected to industrial firms and hospitals, with case studies in reports by Royal Commission, National Research Council, and national ministries of health.

History and research and future prospects

The element’s discovery and early chemistry were advanced by chemists and institutions including Jöns Jakob Berzelius, Morten Thrane Brünnich, George Stoney, Marie Curie, Ernest Rutherford, and research at University of Oslo, University of Uppsala, University of Paris, and University of Cambridge. Cold-war and post–cold-war research pathways involved projects at Oak Ridge National Laboratory, Los Alamos National Laboratory, Argonne National Laboratory, and collaborations with industrial partners like Westinghouse Electric Company and General Electric. Contemporary future prospects are shaped by energy policy bodies and research funding agencies such as the International Energy Agency, European Commission Horizon 2020, national science foundations, venture-backed startups, and university consortia at Massachusetts Institute of Technology, Tsinghua University, Indian Institute of Technology, Imperial College London, and Technical University of Munich. Ongoing work addresses materials science, reactor engineering, fuel-cycle policy, and international safeguards with collaboration across national laboratories, private companies, and multilateral organizations.

Category:Actinides